1. Field of the Invention
This invention relates to a riding tractor for supporting a mower unit, in which engine output is transmitted to a traveling device through a hydrostatic stepless transmission.
2. Description of the Related Art
The above riding tractor is movable back and forth and at varied speeds simply by operating the hydrostatic stepless transmission. This tractor is particularly suited for use as a grass cutting machine.
This type of grass cutting machine is stopped running with the hydrostatic stepless transmission placed in neutral state. On an inclined ground, however, the traveling device could rotate and move the machine inadvertently.
To cope with such a situation, a tractor disclosed in Japanese Patent Laying-Open Publication 2001-63536, for example, has a brake device for acting on wheels constituting a traveling device, and a brake pedal and a brake lever for operating the brake device. The brake lever is maintained in an operative position to maintain the brake device in an operative state. The brake pedal is operable to apply traveling brakes to the traveling device. The brake lever is operable to apply parking brakes to the traveling device. The brake lever for applying the parking brakes has a latch mechanism of the guide groove type. The driver may set the brake lever to a groove for parking to maintain the brake device in the operative state.
There are many advantages where the two brake control tools are provided for operating the brake device, but not a few inconveniences are encountered. When the tractor is stopped or parked on an inclined ground, for example, the tractor may be started, while preventing an inadvertent movement thereof, by shifting the stepless transmission from neutral to a driving state while applying the traveling brakes to the traveling device and adjusting the braking force, depending on an angle of inclination. In the prior art, the braking force must be adjusted by operating the brake pedal. This often results in difficulties in making subtle adjustments.
It may also be disadvantageous in terms of structure and operation to maintain the control lever with the latch mechanism such as a guide groove each time parking brakes are applied.
An object of this invention is to enable brake adjustments to be carried out with ease for applying parking brakes and traveling brakes, in a riding tractor having two brake control tools for one brake device.
Another object of this invention is to a riding tractor for supporting a mower unit, in which a brake pedal and a brake lever acting as brake control tools are hardly obstructive to boarding, alighting or driving.
The above objects are fulfilled, according to this invention, by a riding tractor in which engine output is transmitted to a running device through a hydrostatic stepless transmission, comprising a braking device for acting on the running device, a first brake operating device and a second brake operating device operable independently of each other for operating the braking device, and a brake control device for linking control displacements from the first brake operating device and the second the brake operating device to the brake device, the brake control device including a mechanism movable with the operating devices to maintain the second brake operating device in an inoperative position when the first brake operating device operates the brake device, and a brake lock mechanism switchable between a locking state for locking the brake device to a braking position, and a lock release state, the brake lock mechanism maintaining the lock release position when the first brake operating device operates the brake device, and automatically switching to the locking state when the second brake operating device operates the brake device to the braking position.
When the second brake operating device is operated to actuate the brake device, the brake lock mechanism automatically switches to the locking state for locking the brake device to its operative position. In this state, the second brake operating device is allowed to take braking action. The brake may be applied with a foot when the driver""s hands are used in braking the tractor while controlling the stepless transmission to prevent the tractor from slipping on an inclined ground. Since the first brake operating device moves in response to the second brake operating device, when a parking brake is applied, the first brake operating device may be moved to a position not obstructive to the driver in boarding or alighting from the driving platform.
When the first brake operating device is operated, the brake device may be operated without being locked to the braking position since the brake lock mechanism is maintained in the lock release state.
Thus, a traveling brake may be applied by the first brake operating device. When controlling the stepless transmission and the brake device at the same time, the stepless transmission may be controlled with one hand, the other hand may be used to apply the brake and effect a subtle adjustment of the braking force with ease.
When the traveling brake is applied in this way and the second brake operating device moves in response to the first brake operating device, the driver may have to take care to avoid his or her foot contacting the second brake operating device. However, since the second brake operating device is maintained in the inoperative position, the traveling brake may be applied free of the above inconvenience.
Where the second brake operating device is the foot pedal type for applying a parking brake, the parking brake may easily be applied with a foot even when the hands are used in controlling the stepless transmission or the like. In this case, the first brake operating device may be a hand-operated lever to be rockable to a position not obstructive to the driver so that the driver may board or alight from the driving platform.
In a preferred embodiment of this invention, the brake lock mechanism is releasable by a control displacement of the first brake operating device.
By releasing the brake lock mechanism with the first brake operating device, the brake device unlocked from the operative position. Then, the first brake operating device is operable to apply, release and adjust the braking force of the brake device. As a result, only by operating the first brake operating device, the parking brake may be released and the tractor may be started while controlling the traveling brake.
In another preferred embodiment of this invention, the first brake operating device is a brake lever for applying a traveling brake to the running device, and the second brake operating device is a brake pedal for applying a parking brake to the running device.
With the above construction, the parking brake is applied by operating the brake pedal. The parking brake may be applied with a foot when the driver""s hands are used in braking the tractor while controlling the stepless transmission to prevent the tractor from slipping on an inclined ground.
Since the traveling brake is applied by operating the brake lever, when controlling the stepless transmission and the brake device at the same time, the stepless transmission may be controlled with one hand, the other hand may be used to apply the brake and effect a subtle adjustment of the braking force with ease.
Thus, even when the hands are used in controlling the stepless transmission and the like, the tractor may be parked by applying the parking brake easily with a foot. Further, when starting the tractor on an inclined ground, for example, the stepless transmission may be controlled with one hand, the other hand may be used to apply the brake and effect a subtle adjustment of the braking force with ease, to make a smooth start.
Other features and advantages of this invention will be apparent from the following description of the embodiment to be taken with reference to the drawings.